Ile caseinolytic protease from E. coli is comprised of two subunits ihe protease, CIpP, and the ATPase, CIpA. Fully active CIpP has been over-expressed in R coli and purified to homogeneity. Mass measurements from the STEM indicate that it is a tetradecamer. In stain, it appears as two stacked seven-member rings. Small angle X-ray and neutron scattering curves were determined for ClpP in solution. A model was derived from these data of a cylinder with an axial pore. Ile size of the pore is similar to that found in chaperone proteins. CIpP has been crystallized and the above data. has been used to help solve the x-ray structure. Several cysteine mutants were engineered and Au-labeled and examined in the STEK to aid in the determination of the structure. CIpA has been examined in the STEM. Preliminary samples were not very good but finther attempts with better purified samples are underway. The CIpA component may be hexameric. The final goal is to look at the interaction of CIpP and CIpA.